pam_authtok_check

- authentication and password management module

Synopsis

pam_authtok_check.so.1

Description

pam_authtok_check provides functionality to the Password Management stack. The implementation of pam_sm_chauthtok()
performs a number of checks on the construction of the newly entered
password. pam_sm_chauthtok() is invoked twice by the PAM framework, once with flags set
to PAM_PRELIM_CHECK, and once with flags set to PAM_UPDATE_AUTHTOK. This module only
performs its checks during the first invocation. This module expects the current
authentication token in the PAM_OLDAUTHTOK item, the new (to be checked) password in
the PAM_AUTHTOK item, and the login name in the PAM_USER item. The
checks performed by this module are:

length

The password length should not be less that the minimum specified in /etc/default/passwd.

circular shift

The password should not be a circular shift of the login name. This check may be disabled in /etc/default/passwd.

complexity

The password should contain at least the minimum number of characters described by the parameters MINALPHA, MINNONALPHA, MINDIGIT, and MINSPECIAL. Note that MINNONALPHA describes the same character classes as MINDIGIT and MINSPECIAL combined; therefore the user cannot specify both MINNONALPHA and MINSPECIAL (or MINDIGIT). The user must choose which of the two options to use. Furthermore, the WHITESPACE parameter determines whether whitespace characters are allowed. If unspecified MINALPHA is 2, MINNONALPHA is 1 and WHITESPACE is yes

variation

The old and new passwords must differ by at least the MINDIFF value specified in /etc/default/passwd. If unspecified, the default is 3. For accounts in name services which support password history checking, if prior history is defined, the new password must not match the prior passwords.

dictionary check

The password must not be based on a dictionary word. The list of words to be used for the site's dictionary can be specified with DICTIONLIST. It should contain a comma-separated list of filenames, one word per line. The database that is created from these files is stored in the directory named by DICTIONDBDIR (defaults to /var/passwd). See mkpwdict(1M) for information on pre-generating the database. If neither DICTIONLIST nor DICTIONDBDIR is specified, no dictionary check is made.

upper/lower case

The password must contain at least the minimum of upper- and lower-case letters specified by the MINUPPER and MINLOWER values in /etc/default/passwd. If unspecified, the defaults are 0.

maximum repeats

The password must not contain more consecutively repeating characters than specified by the MAXREPEATS value in /etc/default/passwd. If unspecified, no repeat character check is made.

The following option may be passed to the module:

force_check

If the PAM_NO_AUTHTOK_CHECK flag set, force_check ignores this flag. The PAM_NO_AUTHTOK_CHECK flag can be set to bypass password checks (see pam_chauthtok(3PAM)).

server_policy

If the account authority for the user, as specified by PAM_USER, is not files or NIS, and if server_policy is specified, this module does not perform any password-strength checks. Instead, it leaves it to the account authority to validate the new password against its own set of rules.